Funkmessanlagen der Luftwaffe im Bereich AOK 15

 

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1. LUFTWAFFE RADAR

With the outbreak of the Second World War, radar development became very complex and, from the historian's point of view, it is difficult to provide a complete record of events. On the one hand the needs of the services resulted in separate development to meet their individual requirements, and in each case a different system of code designation was adopted. For reasons of secrecy, and due to a degree of jealousy, inter-service communication was poor, and subsequent development depended significantly on personal contacts between the services and the contractors' scientist. On the other hand the contractors themselves were working for all services and, naturally used ideas developed for the equipment of one service in that of the others. It was only in the second half of the war that attempts were made to introduce a uniform system of designation for radar sets.
Up to this point, there existed no fewer than six different classifications. For example, in the third system introduced, in the surveillance radar FuSE 80 Freya, 'Fu' means Funkmess (radar), 'S' means Siemens (the manufacturer), 'E' refers to the set's function (in this case Erkennung or reconnaissance), '80' is the running number and Freya the set's code word. Sometimes a code was added for the type of installation, e.g. FuSE 62A Würzburg, in which 'A' means stationary ground installation with mechanically rotated aerial; to confuse matters the AA gunners of the time referred to this set as FuMG (Flak) 40T/A.

To make matters worse no fewer than 9 designations for radar types were in existence before 1943. The following table explains this:

FuM Funkmess Radar process - general name
FuMB Funkmessbeaobachtung Radar - detector, passive detection (of enemy radar transmission)
FuME Funkmesserkunnung Radar - detector, active IFF (Identification Friend/Foe)
FuMG Funkmessgerät Radar - anti-aircraft targeting radar
FuMO Funkmessortung Radar - direction finder, active ranging
FuMS Funkmessstörsender Radar - interference sender, active jamming
FuMT Funkmesstäuschung Radar - deceptor, active deception (by transmitting interference signals)
FuMZ Funkmesszusatz Radar - with specialized improvements for various purposes
FuSAn Funksendeanlage Radar - emitter
FuSE Funkmess Siemens Erkennung Radar - detector, active IFF (Identification Friend/Foe)

In 1943 matters improved and most radars were now simply called FuMO by the Kriegsmarine or FuMG by the Luftwaffe, though numerous exceptions remained. On this website we will , therefore, use the 1943 codes, mentioning previous codes only when relevant, as well as the code names.

Along the entire Atlantic and North Sea coasts the Luftwaffe established a chain of radar stations to detect approaching allied aircraft and to direct German fighters towards them. The distance between these stations was calculated in such a way that every coastal airspace was covered by at least one radar station and no incoming aircraft could sneak in undetected. These radar stations were built according to a certain hierarchy, reflecting the importance of the installation. Thus, the follwing installations were distinguished:

Stellung dritte Ordnung 1) Collected radar data (Luftlage) and passed them to the next level up.
2) Did NOT direct own fighter forces
3) Typically equipped with one Freya and 2 Würzburg radars.
Stellung zweite Ordnung 1) Received radar data from the level below and passed them on to the next level up, together with own collected data (Luftlage).
2) Directed own fighter forces.
3) Typically equipped with 2 Freya and 2 Würzburg radars, complemented by 2 long-distance radars (e.g. Wassermann)
Stellung erste Ordnung 1) Received and processed radar data from the levels below and collected own data, thus constructing the so-called Hauptlage.
2) Functioned as the air control centre for a larger area of airspace.
3) From February 1944 onwards, also collected and processed the data of the Flugmeldedienst (Flugwachkommandos) (previously the latter had reported to the Luftgau, thus producing a parallel and inefficient structure).
4) Typically equipped with 2 Freya and 2 Würzburg radars, complemented by 3 long-distance radars (e.g. Wassermann, Mammut, Jagdschloss)

However, this was not yet the end of the process. The Luftlage thus produced was finally passed onto the command centre of the relevant Jagddivision, which could then produce a (Gross)raumlage. In addition, such unit could also direct fighter forces, either through its Jagdfliegerführer (Jafü) for daylight missions or through its Nachtjagdraumführer during darkness.
As can be seen from this information, the decision to launch intercepting fighters could be take on at least three levels. It goes without saying that the highest level would have had to approve all interceptions by fighter forces.

2. OVERVIEW OF MAJOR LUFTWAFFE RADARS

For our purposes it will not be necessary, let alone desirable, to offer a comprehensive overview of Luftwaffe radar systems. We will, therefore, restrict ourselves to a discussion of the most common types: Freya, Würzburg, Würzburg Riese, Wassermann, and Mammut.

2a. The Freya radar

The basic version of this Flugmeldegerät or early-warning radar in modern parlance was the FuSE 80 mass-introduced in 1940. This version had a maximum range of 200 kilometres and could only measure distance and direction of approaching aircraft, which was also its main weakness as it required other radars for exact measurements of location, course and height. This basic version was intstalled in nearly all Luftwaffe radar stations within the area of AOK 15.
Later versions, such as the FuMG 450 Freya A/N and the FuMG 401 Freya LZ (introduced in 1941-42) enabled a small increase in range (up to 250 kilometres for the latter), but especially offered a better resolution (between 10-20 times better).
Another interesting variant was the FuMG 401 Freya Fahrstuhl, introduced in 1942. Here the radar could slide up or down along vertical railings. This system prevented high-flying approaching aircraft from disappearing in the ground reflection nulls of the vertical plane directional pattern while at the same time providing a rough estimation of the altitude. One one these was located within the area of 15 AOK in Ste-Cécile plage.
In total, the Freya concept gave rise to at least 11 different versions (with many more sub-versions), only one of which is of immediate interest to us.
In 1941 the first experiments were carried out with 2 Freya radar systems in directing fighters using the so-called Erstling method. This involved one radar tracking the enemy, while the other plotted the German fighter. In 1943 this system was replaced by the FuSAn 730 Freya EGON system, with EGON being short for Erstling-Gemse-Offensiv-Navigationsverfahren. Part of this system were the Kuh and Gemse systems. Both were IFF (Identification Friend or Foe) systems. Simply put the Kuh system was the sender, while the Gemse system was the receiver of the IFF signal.

 
FuSE 80  FuMG 450 Freya A/N FuMG 401 Freya LZ  FuMG 401 Freya Fahrstuhl 

2b. The Würzburg radar

Beginning on 1937 the German company Telefunken became involved in the development of a small radar system for short-range location and identification. This was the FuMG 39 T Würzburg A. In the fall of 1939 the system was introduced in the Luftwaffe with the designation FuMG 62 Würzburg. The radar had a small parabolic dish with a diameter of 3 metres and had a range of up to 40 kilometres, with an accuracy of 80-120 metres and an azimuth/height accuracy of 1.5-2°. Yet, these capabilities were not judged sufficient.
The system was either modified or built from the outset as the FuMG 62 Würzburg C with a precision send-and-receive signal kit (the C-Zusatz) developed by Telefunken in 1940. In place of a fixed dipole the system was now fitted with a running dipole, which gave it an azimuth acuracy of 0.45° and a vertical accuracy of 7-9/16°.
With the introduction of the EAG 62 Emil "D-Zusatz" distance measuring accuracy was improved to 25-40 metres and, at the same time, provided a direct feed of ranging data to the ranging processor of the Überträgungsgerät 37, from where the data would be sent to a Flak batterie command and control system. The system, known as the FuMG 62 Würzburg D began arriving at the front in 1942. By the end of the war, approximately 4,000 systems had been manufactured, making it the standard Flakzielgerät radar system with the Flak forces.

FuMG 62 Würzburg A FuMG 62 Würzburg C FuMG 62 Würzburg D

2c. The Würzburg Riese radar

It is appropriate that this Flugmeldegerät radar should be discussed at this point since the FuMG 65 Würzburg Riese was developed from the FuMG 62 D discussed above, with which it shared its electrical ranging components. To increase the range to 50-70 km, the system was fitted with a much larger dish with a diameter of 7.5 metres. This enabled aircraft to be tracked out to 40-60 km, with raids being acquired as far out as 80 km. Range accuracy was 15-20 metres, with an azimuth and vertical accuracy of 0.2° and 0.1°, respectively, the system was suitable for a variety of roles and particularly liked by both the Luftwaffe and the Kriegsmarine.
The radar construction rested on a pivot shaft, itself having a concrete base, these days often the only reminder of the presence of the radar. The distinctive operations van and the tip mechanism and dish opposite virtually balanced each other out as they rotated around the pivot shaft.
Typically, the Würzburg Riese would operate jointly with a Freya radar, balancing out each other's weaknesses. As mentioned above, the Freya was able to pick up targets from far out but needed the Würzburg Riese for exact measurements of location, course and height. Inversely, the Würzburg Riese required the Freya not only for distance, but also when faced with rapidly-moving targets. The latter problem, however, could be resolved to some extent by fitting the Würzburg with a Freya supplemental search kit, called the GEMA Zusatz.

FuMG 65 Würzburg Riese 

 

3. The Wassermann and Klein Heidelberg radars

Just after the outbreak of the war a requirement was issued for a radar system for early warning the range of which would be significantly greater than that of the Freya. In order to meet this requirement, four Freya antennas were initially set up on top of each other on a 36-meter high mast, which in turn was mounted to a rotating stand. This was the Wassermann leicht model (FuMG 41) with a range of 200 km and an azimuth accuracy of +/- 4°.

The Wassermann schwer model (FuMG 42) had double the number of antenna fields, attached to a distinctive  self-supporting steel tube rotating tower with a diameter of 4 metres and a height of 60 metres. Its range was around 300km with an azimuth accuracy of +/- 3°.

The firm of Siemens started to produce improved variants of the radars from 1942 onwards. Its first Wassermann MI (FuMG 402 I) had a 36-meter high mast and was similar in design to the L version, albeit with improvements.

The transmitter mast for the Wassermann MII radar (FuMG 402 II) was 40 meters high and had a wider, horizontally polarized antenna plus an IFF system.

Finally with the Wassermann MIII and MIV models (FuMG 402 III and IV) the operations van was locates in the centre of the former's 51-meter and the latter's 60-meter high masts. Its range was 300 km, although over water 380km could be reached. However, azimuth accuracy was only +/- 25°.

 

Wassermann leicht Wassermann schwer Wasssermann MI Wassermann MII Wassermann MIV

At this point mention should also be made of a sophisticated German radar system, i.e. the Klein Heidelberg. For reasons of camouflage it was fitted to the back of a Wassermann schwer antenna, as the picture below shows. It was given an supplemary name of Parasit because it could also be used to detect those aircraft which the British were tracking. This was possible necause the transmitting waves which the British were sending were known and these were not only reflected back in the direction of the transmitter. The detection range was around 250km, range accuracy was between 1-2km and azimuth accuracy was initially +/3°, but later +/-1°. The major advantage of the system was it functioned smoothly even when the enemy used jamming signals and chaff countermeasures.

Wassermann schwer with Klein Heidelberg antenna
Interestingly, the Klein Heidelberg does not appear on the German map of June 1944, detailing all Luftwaffe radar installations in Western Europe. The exact reason for this remains a mystery. Either the radar system was so secret that it was deliberately not mentioned or someone genuinely mistakenly forgot to include it.

3. The Mammut radar

The GEMA company also became involved in the development of early warning type radars. Its FuMG 41G Mummut I had four masts in a row. Attached to these were 8 Freya antennas which together made up a surface of 10 meters tall and 25 meters wide. The Mammut II also had four masts but the antennas covered an area of 11.1 by 28.5 meters. The radar was able to pick up targets at around 8000 meters out to a range of 300 km. Low-flying targets at around 50 meters' height were acquired at around 35 km. Range accuracy was +/-300 m and azimuth accuracy +/-0.5°. Finally, it is also worth mentioning at this point that the Kriegsmarine radars had only 3 masts instead of four.

FuMG 41G Mammut

        

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